I had the same problem when I installed Lubuntu Next 17.10.
I also had to install the "lightdm-gtk-greeter-settings" package, as it was not included. (I don't know if this is true of both LXDE and LXQt versions of 17.10, or just LXQt..).
I had the same problem when I installed Lubuntu Next 17.10.
I also had to install the "lightdm- gtk-greeter- settings" package, as it was not included.
(I don't know if this is true of both LXDE and LXQt versions of 17.10, or just LXQt..).